diff --git a/core/src/main/java/hudson/Functions.java b/core/src/main/java/hudson/Functions.java
index d0849ed81c..ee85b07f56 100644
--- a/core/src/main/java/hudson/Functions.java
+++ b/core/src/main/java/hudson/Functions.java
@@ -12,6 +12,7 @@ import hudson.model.Action;
 import org.kohsuke.stapler.Ancestor;
 import org.kohsuke.stapler.StaplerRequest;
 import org.kohsuke.stapler.StaplerResponse;
+import org.apache.commons.jexl.parser.ASTSizeFunction;
 
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletRequest;
@@ -366,4 +367,13 @@ public class Functions {
         else
             return "images/24x24/"+name;
     }
+
+    /**
+     * Works like JSTL build-in size(x) function,
+     * but handle null gracefully.
+     */
+    public static int size(Object o) throws Exception {
+        if(o==null) return 0;
+        return ASTSizeFunction.sizeOf(o);
+    }
 }